This invention relates to an activated sludge system, i.e. to the biological purification of wastewater, e.g., sewage, wherein the wastewater is treated in a reactor in the presence of sludge, optionally with the absorption of air and/or oxygen, and subsequently the mixture of treated wastewater and activated sludge is separated into purified water and sludge.
In conventional biological wastewater treatment processes, such as activation, nitrification or denitrification processes, it is necessary to separate in a downstream secondary settling tank the purified wastewater from the biomass formed by the activity of special microorganisms suspended in the wastewater as well as in the solids contained in the incoming wastewater as well as in the solids contained in the incoming wastewater. Even in the more recent wastewater treatment processes, in which the microorganisms responsible for the biological conversion are fixed on support materials, such as for example, sand, activated charcoal or polymeric foam particles, it is necessary to include a secondary settler and/or a regenerating installation for the support particles; otherwise, upon the design load being occasionally exceeded, an undesirable formation of unfixed biomass would occur, thereby detrimentally affecting the quality of the purified wastewater effluent. The installation of a downstream secondary sedimentation tank or regenerator for the support particles is, however, expensive and requires additional land, which in the case of wastewater purification is not an insignificant factor in view of the huge equipment sizes involved. In one attempt to solve this problem, a cyclically operated compressor chamber is suggested for regeneration, U.S. patent application Ser. No. 467,007, filed Feb. 16, 1983 by Uwe Fuchs, one of the co-inventors of this invention, said application being incorporated by reference herein; nevertheless, this suggested solution to the problem is less than ideal for activated sludge systems.